Problem: Ishaan is $3$ times as old as Christopher and is also $14$ years older than Christopher. How old is Ishaan?
Explanation: We can use the given information to write down two equations that describe the ages of Ishaan and Christopher. Let Ishaan's current age be $i$ and Christopher's current age be $c$. ${i = 3c}$ ${i = c + 14}$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $i$ is to solve the second equation for $c$ and substitute that value into the first equation. Solving our second equation for $c$, we get: ${c = i - 14}$. Substituting this into our first equation, we get the equation: ${i = 3}{(i - 14)}$ which combines the information about $i$ from both of our original equations. Simplifying the right side of this equation, we get: $i = 3i - 42$. Solving for $i$, we get: $2 i = 42$. $i = 21$.